Conventionally, a centrifugal compressor configured to return a portion of a working fluid that passes through an impeller to an intake is known. For example, Patent Literature 1 discloses a centrifugal compressor 100 as shown in FIG. 7.
In this centrifugal compressor 100, a cylindrical treatment chamber 130 is provided in a shroud wall 120 surrounding an impeller 110. A slit-like first flow path 131 opens towards the impeller 110 at one end of the treatment chamber 130, and a slit-like second flow path 132 opens into an intake 101 at the other end of the treatment chamber 130.